植物乳杆菌β-半乳糖苷酶催化合成低聚半乳糖及其体外乳酸菌增殖活性

Enzymatic Production and Lactobacillus Proliferation of Galactooligosaccharidesby β-Galactosidase from Lactobacillus plantarum in vitro

摘要:

利用植物乳杆菌来源的β-半乳糖苷酶合成低聚半乳糖（galactooligosaccharides，GOS），通过对乳糖浓度、反应温度、体系pH以及酶浓度等反应条件及其体外增殖乳酸菌（lactic acid bacteria，LAB）进行研究，确定酶法合成GOS及其各主要组分产量的最优条件并表征其益生功效。结果表明：乳糖浓度和反应温度的变化对于产物合成影响较大，为主要影响条件，而体系pH和酶浓度对于各产物最高产量的影响不显著，为次要影响条件。经过对反应条件进行优化，总产量与各组分产量的最优条件一致，为底物浓度400 g/L，体系pH 7.0，10 U/mL的酶浓度，45 ℃水浴10 h。总GOS产量达到177.26 g/L，在体系中占44.31% （m/V）。其中异乳糖、6′-半乳二糖、6′-GOS和3′-GOS的产量分别是63.22 g/L、15.32 g/L、72.21 g/L和25.11 g/L。相比较主要以β(1→4)糖苷键连接的商业化低聚半乳糖（QHT-GOS），半乳糖残基以β(1→6)糖苷键连接为主的新合成GOS对于供试LAB增殖作用更为显著，表现在以较低的低聚糖比例（44.3%）达到与之高比例低聚糖（70%）相当的LAB生长密度，以及具有明显优势的最大比生长速率。

Abstract:

Enzymatic synthesis of prebiotic galactooligosaccharides (GOS) using the β-galactosidases produced from Lactobacillus plantarum was investigated. In this work, the effects of synthetic conditions including concentration of lactose substrate, reaction temperature, pH of system, enzyme concentration on the formation and the monitoring of the proliferation of lactic acid bacteria in vitro, total output and optimum conditions of different pure components of GOS were evaluated. Its probiotic activity was characterized. The results showed that the major reaction conditions were concentration of substrate, temperature, whereas pH and concentration of enzyme were secondary conditions. The optimal conditions for the total output was listed as followed: 45°C, substrate concentration of 400 g/L, pH 7.0, enzyme concentration of 10 U/mL, time of 10 h. Under these conditions, the total GOS output was 177.26 g/L, accounted for 44.31% (m/V) in the reaction system, including allo-lactose, 6′-galactobiose, 6′-GOS and 3′-GOS, they were 63.22 g/L, 15.32 g/L, 72.21 g/L and 25.11 g/L, respectively. For the proliferation of lactic acid bacteria in vitro, the new GOS was more remarkable by comparison to the commercialized GOS, as exhibited in the same amount of microbodies at relatively low concentration of GOS and the obvious advantage of maximum specific growth rate.